docs: def df_representative_sequences(self):
          """DataFrame: Pandas DataFrame of representative sequence information per protein."""
  
          seq_mapping_pre_df = []
          df_cols = ['gene', 'uniprot', 'kegg', 'num_pdbs', 'pdbs', 'seq_len', 'sequence_file', 'metadata_file']
  
          for g in self.genes_with_a_representative_sequence:
              gene_dict = g.protein.representative_sequence.get_dict(df_format=True, only_attributes=df_cols)
              gene_dict['gene'] = g.id
              seq_mapping_pre_df.append(gene_dict)
  
          df = pd.DataFrame.from_records(seq_mapping_pre_df, columns=df_cols).set_index('gene')
          if df.empty:
              log.warning('Empty dataframe')
              return df
          else:
              return ssbio.utils.clean_df(df)